Synaptic alterations in pyramidal cells following genetic manipulation of neuronal excitability in monkey prefrontal cortex.

In schizophrenia, layer 3 pyramidal neurons (L3PNs) in the dorsolateral prefrontal cortex (DLPFC) are thought to receive fewer excitatory synaptic inputs and to have lower expression levels of activity-dependent genes and of genes involved in mitochondrial energy production. In concert, these findings from previous studies suggest that DLPFC L3PNs are hypoactive in schizophrenia, disrupting the patterns of activity that are crucial for working memory, which is impaired in the illness. However, whether lower PN activity produces alterations in inhibitory and/or excitatory synaptic strength has not been tested in the primate DLPFC. Here, we decreased PN excitability in rhesus monkey DLPFC in vivo using adeno-associated viral vectors (AAVs) to produce Cre recombinase-mediated overexpression of Kir2.1 channels, a genetic silencing tool that efficiently decreases neuronal excitability. In acute slices prepared from DLPFC 7-12 weeks post-AAV microinjections, Kir2.1-overexpressing PNs had a significantly reduced excitability largely attributable to highly specific effects of the AAV-encoded Kir2.1 channels. Moreover, recordings of synaptic currents showed that Kir2.1-overexpressing DLPFC PNs had reduced strength of excitatory synapses whereas inhibitory synaptic inputs were not affected. The decrease in excitatory synaptic strength was not associated with changes in dendritic spine number, suggesting that excitatory synapse quantity was unaltered in Kir2.1-overexpressing DLPFC PNs. These findings suggest that, in schizophrenia, the excitatory synapses on hypoactive L3PNs are weaker and thus might represent a substrate for novel therapeutic interventions. Significance Statement: In schizophrenia, dorsolateral prefrontal cortex (DLPFC) pyramidal neurons (PNs) have both transcriptional and structural alterations that suggest they are hypoactive. PN hypoactivity is thought to produce synaptic alterations in schizophrenia, however the effects of lower neuronal activity on synaptic function in primate DLPFC have not been examined. Here, we used, for the first time in primate neocortex, adeno-associated viral vectors (AAVs) to reduce PN excitability with Kir2.1 channel overexpression and tested if this manipulation altered the strength of synaptic inputs onto the Kir2.1-overexpressing PNs. Recordings in DLPFC slices showed that Kir2.1 overexpression depressed excitatory (but not inhibitory), synaptic currents, suggesting that, in schizophrenia, the hypoactivity of PNs might be exacerbated by reduced strength of the excitatory synapses they receive.

Machine learning sequence prioritization for cell type-specific enhancer design.

Recent discoveries of extreme cellular diversity in the brain warrant rapid development of technologies to access specific cell populations within heterogeneous tissue. Available approaches for engineering-targeted technologies for new neuron subtypes are low yield, involving intensive transgenic strain or virus screening. Here, we present Specific Nuclear-Anchored Independent Labeling (SNAIL), an improved virus-based strategy for cell labeling and nuclear isolation from heterogeneous tissue. SNAIL works by leveraging machine learning and other computational approaches to identify DNA sequence features that confer cell type-specific gene activation and then make a probe that drives an affinity purification-compatible reporter gene. As a proof of concept, we designed and validated two novel SNAIL probes that target parvalbumin-expressing (PV+) neurons. Nuclear isolation using SNAIL in wild-type mice is sufficient to capture characteristic open chromatin features of PV+ neurons in the cortex, striatum, and external globus pallidus. The SNAIL framework also has high utility for multispecies cell probe engineering; expression from a mouse PV+ SNAIL enhancer sequence was enriched in PV+ neurons of the macaque cortex. Expansion of this technology has broad applications in cell type-specific observation, manipulation, and therapeutics across species and disease models.

Oral hygiene behaviours and readiness to change using the TransTheoretical Model (TTM).

OBJECTIVE: The aim of this pilot study was to investigate the Transtheoretical Model (TTM) in relation to measures of readiness to change oral hygiene behaviours. RESEARCH DESIGN: Participants (N = 105) were recruited from a dental hygiene patient waiting list. A self-administered questionnaire was designed; it included four measures related to inter-dental cleaning used for TTM staging, confidence and frequency measures of future interdental cleaning and toothbrushing, together with items seeking demographic details. Data collection occurred before a dental hygiene appointment where oral health advice was offered, and then at three and six months afterwards, in order to measure readiness to change post-intervention. RESULTS: All three questionnaires were returned by 91.4% of participants. The confidence measures for maintaining toothbrushing twice per day and for interdental cleaning were associated with TTM staging at baseline (respective correlation coefficients of 0.200; P = 0.042 and 0.584; P < 0.001). Participants were likely to be in a higher TTM stage at 3 months after attendance at the dental hygiene clinic and then decline to a lower TTM stage by 6 months (baseline to 3 months and 6 months: Wilcoxon signed rank tests of p= 0.024 and p = 0.627). Of the 31 participants (33%) who improved their TTM staging between baseline and 3 months, 11 (35%) fell back to a lower category between 3 months and 6 months, 14 (45%) maintained their improvement, and 6 (19%) improved further. CONCLUSIONS: Understanding a person's readiness to change could improve the way in which oral hygiene interventions and advice are given in the clinical setting. The TTM staging measurement tool used here provides insight into people's readiness to change their oral hygiene behaviours, and its use would aid practitioners in the delivery of oral health messages. The initial improvement in TTM stage and subsequent regression was consistent with the TTM's relapse phenomenon and reinforces the concept that on-going support is crucial to maintaining behaviour change.